What You Need to Know About GM's New HD Steering Assist
Wireless phone charging, a factory-installed gooseneck/fifth-wheel trailer hitch and locking a tailgate with the key fob are all available features heavy-duty pickup truck buyers will find appealing in Chevrolet's 2016 Silverado 2500/3500 and GMC's 2016 Sierra 2500/3500 models. Even the most advanced technophiles will appreciate the ability to access more apps directly from their cellphones through the new 8-inch touch-screen's Apple CarPlay and Android Auto option.
But the best available feature for the 2016 Silverado/Sierra HDs is not what you see or hear — it's what you feel while through the steering wheel courtesy of Digital Steering Assist, a new technology from GM (not available on Work Truck trims or regular cab models).
DSA is a computer-controlled hydraulic variable-assist steering system that makes GM HD pickups feel just as nimble as their half-ton counterparts, which have programmable electric power steering.
We had the opportunity to talk with Mike Symons, global vehicle performance manager for GM trucks, about DSA during a recent ride-and-drive event featuring Chevrolet HD pickups and the new 2016 Colorado with the Duramax diesel engine.
PickupTrucks.com:How does this new Digital Steering Assist technology make the 2016 models drive differently than previous versions?
Symons: Compared to a normal hydraulic system [or recirculating ball] that's in our older HDs, the new models have Digital Steering Assist that adds a torque overlay to allow heavy-duty users to get some of the same advantages they would get on the light-duty pickups with electronic power steering. Essentially what we've given the HDs is an electronically controlled variable-assist hydraulic power steering setup that reduces the amount of work the driver exerts to steer and control the truck depending on speed and other inputs. As a result, the truck feels easier to control, especially with better stability at higher speeds or on surfaces such as crowned roads or areas with constant crosswinds.
PUTC:Why not put heavier-duty electronic power steering in the HDs like GM has in the half-ton and midsize pickups?
Symons: The EPS rack-and-pinion components aren't robust enough to handle the weights and steering loads heavy-duty pickups place on them. That's why we've stayed with hydraulic recirculating ball steering systems in the HD and added Digital Steering Assist. It's the best of both worlds.
PUTC:How does DSA make steering easier?
Symons: What we have done is overlay the standard [hydraulic] steering system with two additional computer-controlled valves within the steering pump that add or subtract torque [via fluid pressure] depending on the software parameters that have been established. What that essentially provides is speed-variable assist — offering a lighter turning effort at lower speeds and heavier, slower responses at higher speeds to enhance directional control and stability.
PUTC:How does the DSA know how to make those adjustments?
Symons: The system gets its data from multiple sensors in the truck, including wheel speeds and in the steering wheel, that sense if it's being pulled over time in one direction or another. That data shows how much effort the driver is putting on the steering wheel and how fast or slow the truck is moving. The algorithms within the Digital Steering Assist make continuous changes accordingly so the driver isn't constantly fighting with or needing to provide the same inputs into the steering wheel.
PUTC:What are examples of the differences owners of older HD models would feel when driving a 2016 Silverado HD equipped with DSA?
Symons: [Something] someone familiar with driving an older HD would feel right away is how light the new truck's steering feels during low-speed trailering or parking lot maneuvers. They will also notice how quickly and easily the steering wheel returns to center after those hard lock-to-lock steering maneuvers. We call that active returnability assist. The idea is to give a nice, consistent steering feel similar to that of a light-duty pickup in a heavy-duty package.
PUTC:Is there a big difference at highway speeds?
Symons: Yes, that's another area we spent a lot of time with the DSA overlay. Drivers will notice the 2016 HD requires far less steering effort to compensate for driving in strong crosswinds or on long stretches of crowned road or highway. This system actually learns as you drive and adjusts the steering assist accordingly. For example, Digital Steering Assists' "pull compensation" programming recognizes when a hydraulic pressure offset is required while driving on a sloped road or in those prolonged crosswinds you find across the Midwest. The computer adds more hydraulic torque to the steering pump to help compensate so the driver doesn't have to put in as much steering input. The truck drives straighter, requires less input from the driver and, as a consequence, the driver is less fatigued when he gets to his destination.
PUTC:Does DSA make any changes to steering when the truck is in Tow/Haul mode?
Symons: Yes. That's the beauty of DSA and how the integrated computer technology really benefits those who tow trailers. When Tow/Haul is activated, we've optimized the system so the [steering] effort curve is changed accordingly. DSA adds a little more assist to the slow-speed steering maneuvers, so when backing up a bigger trailer you'd get lighter steering than you would in a non-Tow/Haul mode. Conversely, on the highway when in Tow/Haul mode, the truck will actually take away some assist, making steering effort a little higher, which helps improve trailer control and stability when pulling a big trailer.
PUTC:Does DSA help compensate for an improperly setup trailer with too little or too much tongue weight on the truck?
Symons: We don't have any type of sensing in the suspension, so there's no way to monitor front or rear axle loads, but that's a great idea. However, Digital Steering Assist's increased effort curve in Tow/Haul mode will help to some degree, but the system is not set up for those types of unsafe situations.
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